If you're just starting with Chivalry modding, check out the /wiki/spaces/CHIV/pages/13336690 page.
If you're just starting with learning to code in UnrealScript for Unreal Engine 3, your main resources will be:
Important UDN pages:
Supplementary documentation here on our Wiki:
If you'd like to see an example of a Chivalry mod, check out:
In terms of programming in general, you'll want to be at least familiar with Object-Oriented Programming, which is the paradigm that UnrealScript follows. That's beyond the scope of this document, but there are many resources, courses, books, etc. out there on the topic.